Summary

Decide your targets and prepare starlists

  1. Create and format your target list (``starlist'') as described here.

Find your cross disperser and grating angles

  1. Although HIRES covers a wavelength range between 0.3 and 1 micron, that wavelength range cannot be covered in the same exposure simultaneously. Thus, identify first the wavelength of spectral lines you are interested on having on each HIRES exposure.
  2. Use the Echelle format simulator to select the blue or red crossdisperser. Then, locate the wavelength of your spectral lines of interest for your science in the echelle orders.
  3. Slide the box with the position of the three HIRES CCD over the picture of the echelle orders and decide the position or positions that cover the spectral lines you are interested in.
  4. On the right side of the echelle picture, the simulator will show the echelle angles and cross disperer angles needed to have the configuration of the instrument as shown in the echelle picture.
  5. Write down the cross disperser and grating angles you need for each of your targets.

Choose the most convenient filters for your science and the guider

  1. The wavelength coverage of each of the science, and guider filters are presented here. Decide the filters you are interested in before your observation.

Find out if you need to use the iodine cell

    The iodine absorption cell is used to create a fiducial wavelength scale for very precise (m/s) radial velocity measurements. Most iodine features are located between 5000 and 6200 Angstroms, ideal for radial velocity determinations of late-type stars. The iodine cell is physically located in front of the decker plate and can moved in and out of the optical beam via keywords or using XHIRES. To use the iodine cell, it must first be turned on from the HIRES control pulldown menu (right click in background, HIRES control menu, start iodine cell). This will begin warming the cell to its nominal operating temperature. Two temperatures are displayed in an XSHOW GUI: TEMPIOD1 and TEMPIOD2. The former is typically around 65 C and represents the temperature at the outer edge of the cell. The latter is maintained near 50 C and represents the temperature near the center of the cell. Allow at least 45 minutes for the iodine cell to warm up to these nominal values before use.

Estimate your exposure times

  1. Use the HIRES Exposure Time Calculator to determine the exposure time for each of your targets.

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